JPH1031381A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing the occurrence of staggering and jettering of a recording paper caused by the inclination of a heat roller. SOLUTION: In this fixing device, each outside diameter on a both end parts in axial direction of a press roller 50 and the heat roller 40 is formed larger than each outside diameter of respective parts between both end parts of the press roller 50 and the heat roller 40 by specific amounts, and the interval in the axial direction between both ends is set wider than the width of a recording paper, so that when the heat roller 40 and the press roller 50 come to close, the larger diameter parts of the press roller 50 abuts on the heat roller 40, shifts it and holds and recording paper there between after the heat roller 40 becomes in parallel with the press roller 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an image such as a toner image on recording paper in a printer or the like which forms an image by an electrophotographic method.

[0002]

2. Description of the Related Art A fixing device for fixing a toner image transferred to a recording sheet is provided in a printer or the like which forms an image by using an electrophotographic method. The fixing device fixes the toner image on the recording paper by pressing and heating the recording paper between a heat roller having a built-in heat source and a press roller having a surface made of an elastic material.

In general, the recording paper transport path is provided horizontally, and therefore, the heat roller and the press roller are arranged so as to sandwich the recording paper from above and below. Also, if the recording paper is stopped and is in contact with the heat roller, the recording paper will dry abnormally.Therefore, conventionally, the press roller is moved in the direction of approaching and separating from the heat roller, and the heat roller and the press roller are moved. An opening and closing mechanism is provided to open and close the space.

[0004] In recent years, a fixing device has been proposed in which a heat roller and a press roller, which are consumable parts, are detachable units with respect to the opening / closing mechanism and the like, which are non-consumable parts. The non-consumable parts also include a rotation mechanism for driving the heat roller to rotate. In such a fixing device, the attachment / detachment unit is attached / detached vertically so as not to take up space in the recording paper conveyance direction (horizontal direction). And
When the detachable unit is mounted from above, a driven gear provided on the heat roller is configured to engage with a drive gear of a rotating mechanism disposed below the driven gear.

[0005]

Here, when the heating of the heat roller is started, the heat roller body is first heated, then the bearing holding the support shaft of the heat roller is heated, and then the frame holding the bearing is heated. Heated. Therefore, a clearance is provided between the support shaft and the bearing to absorb the thermal expansion of the support shaft that is heated first, and between the bearing and the frame, the thermal expansion of the bearing that is heated first. Clearance is provided for absorbing the air.

Accordingly, when the driving gear of the rotating mechanism rotates, the driven gear is urged by the engagement between the driving gear and the driven gear, and one end of the heat roller on the driven gear side is lifted by the clearance. That is, the heat roller is inclined with respect to the press roller. When the press roller is closed in this state, one end in the width direction of the recording paper is caught earlier than the other end, but since the press roller is stopped, the one caught first is braked. That is, there is a problem that the recording paper is skewed because one end that is closed later is conveyed before the other end (the one that is closed earlier). In particular, when continuous recording paper is used as recording paper, skew may accumulate as the page advances, and skew may develop.

In a printer or the like that uses continuous recording paper as a recording paper, when the recording paper is sandwiched between a heat roller and a press roller, a toner image is printed on a subsequent page in a transfer section located upstream of the fixing device in the recording paper conveyance direction. Is being transferred. Here, since the press roller is stopped at the retracted position, the recording paper stops momentarily when the recording paper is sandwiched between the heat roller and the press roller. Along with this, the recording paper in the transfer section on the upstream side in the transport direction stops for a moment, and the position of the toner image transferred to the recording paper fluctuates in the transport direction of the recording paper, so-called jitter may occur.

An object of the present invention is to provide a fixing device capable of preventing the skew of recording paper and the occurrence of jitter due to the inclination of a heat roller in view of the above circumstances.

[0009]

In order to solve the above-mentioned problems, a fixing device according to the present invention comprises a heat roller having a built-in heat source, a press roller for pressing recording paper between the heat roller, and a heat roller. Opening and closing means for relatively moving the two rollers to open and close between the press roller and the press roller, wherein the heat roller is displaceably held within a predetermined range in the direction of the relative movement, and the axial direction of the press roller or the heat roller is provided. The outer diameter of both ends is formed larger by a predetermined amount than the outer diameter of the portion sandwiched between the both ends, and the axial distance between the both ends is set to be larger than the width of the recording paper. Things.

With this configuration, when the heat roller and the press roller approach each other, the large-diameter portion of the press roller comes into contact with and displaces the heat roller, and after the heat roller becomes parallel to the press roller. Insert the recording paper. Accordingly, since the recording paper is evenly sandwiched in the width direction, skewing of the recording paper is prevented.

It is also possible to further comprise a rotating means for rotating the heat roller before closing the space between the heat roller and the press roller. With such a configuration, when the recording paper is pinched between the rotating heat roller and the stopped press roller, the recording paper is Stopping is prevented. That is, occurrence of jitter caused by a momentary stoppage of transport is prevented.

Further, a predetermined clearance is provided between a support shaft of the heat roller and a bearing for holding the support shaft, and between the bearing and a holding member for holding the bearing.
The clearance is provided to absorb a difference in thermal expansion between the support shaft, the bearing, and the holding member when heating the heat roller is started.

Further, the press roller can be disposed vertically below the heat roller. Further, the opening and closing means may be configured to move the press roller in a direction approaching and away from the heat roller. The heat roller and press roller are
It is also possible to attach it to a frame that is detachable from the fixing device.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fixing device according to the present invention will be described below. Printer 1 shown as an embodiment
Is a printer that forms an image on a recording sheet P, which is a continuous recording sheet, using a so-called electrophotographic method.

First, a schematic configuration of the printer 1 will be described. FIG. 1 is a side view showing a schematic configuration of the printer 1. 1, a printer 1 includes a scanning optical device 15 that irradiates a laser beam modulated in accordance with image information, a photosensitive drum 16 that forms a latent image by light emitted from the scanning optical device 15, a photosensitive drum 16, A charging unit 17 for uniformly charging the toner image 16, a developing unit 18 for developing the latent image with toner, a transfer unit 20 for transferring the toner image to recording paper, and a fixing device 30 for fixing the toner image to recording paper P. , Housed in the housing 10.

The image is formed as follows. The laser light modulated according to the image information is applied to the scanning optical device 1
5, and the surface of the photosensitive drum 16 is exposed. The photosensitive drum 16 on the surface of the photosensitive drum 16 is uniformly charged by the charging unit 17 and exposed to the modulated laser light to form a latent image. The developing unit 18 applies toner to the latent image formed on the surface of the photosensitive drum 16 to form a toner image. The toner image on the surface of the photosensitive drum 16 is transferred to the recording paper P by discharging the corona charger 19 in the transfer unit 20, and the recording paper P
The toner image transferred onto the recording paper P is fixed by pressing and heating by the fixing device 30. The residual toner remaining on the surface of the photoconductor drum 16 is removed by the cleaning unit 13, and the surface of the photoconductor drum is neutralized by the neutralization unit 14 to prepare for the next image formation.

The recording paper P is inserted from an insertion opening 11 formed on the right side of the housing 10 in the drawing, and
0, passes through the fixing device 30, and is discharged from the discharge port 12 provided on the left side of the housing 10 in the figure. The recording paper P is
The sheet is conveyed by a tractor unit 60 provided between the transfer unit 20 and the fixing device 30. Tractor unit 60
A tractor belt 61 having projections engaging with feed holes provided at both ends in the width direction of the recording paper P is connected to a pair of pulleys 62.
And the pulley 62
Is driven by a tractor motor 84.

The tractor motor 84 and the fixing device 3
0, and a main motor 86 that rotates the photosensitive drum 16 and the like.
Is controlled by

An upper portion of the housing 10 is an upper housing 10a which can be swingably opened, and a scanning optical device 15 is housed in the upper housing 10a. Therefore, the user can swing open the upper housing 10 a and face the fixing device 30 or the tractor unit 60 from above the printer 1.

The fixing device 30 includes a heat roller 40 having a built-in heat source and a press roller 5 having a surface made of an elastic material.
0 is provided. Further, the fixing device 30 is provided with an opening and closing mechanism 33 for opening and closing the heat roller 40 and the press roller 50. The opening / closing mechanism 33 moves the press roller 50 between an operation position for pressing the recording paper P with the heat roller 40 and a retracted position retracted from the operation position.

Here, in the transfer section 20, the corona charger 19 is supported by a swing holder 22 which is swingably provided by a swing shaft 21, and an action position close to the surface of the photosensitive drum 16, It is possible to move between the evacuated position and the separated position. The swing holder 22 swings by a slide arm 23 driven by an opening / closing mechanism 33.

A discharge roller section 70 for discharging the recording paper P is provided between the fixing device 30 and the discharge port 12. The discharge roller unit 70 includes an upper roller 71 and a lower roller 72 disposed above and below the recording paper P. The upper roller 71 moves in cooperation with the opening / closing mechanism 33 between an operation position where the recording paper P is sandwiched between the lower roller 72 and a retracted position retracted from the operation position.

The printer 1 allows the user to separate or visually confirm the page on which the image has been formed.
When the image forming process is completed, the page on which the image has been formed on the recording paper P is temporarily discharged out of the printer 1. Then, when performing the next image formation, the recording paper P is pulled back and the image formation is restarted. Therefore, when the recording paper P is pulled back or stopped, the opening and closing mechanism 33 causes the press roller 50, the corona charger 19, and the upper roller 7.
1 move to the retreat position to open the conveyance path of the recording paper P.

Next, the details of the fixing device 30 will be described. In the fixing device 30, the heat roller 40 and the press roller 50, which are consumable parts, are held by a detachable unit 32 that is detachable from the printer 1. The detachable unit 32 is opened by the user opening the upper housing 10a. , Can be removed upward.

FIG. 2 is a perspective view showing the detachable unit 32. As shown in FIG. 2, the attachment / detachment unit 32 has an upper frame 120 and a lower frame 130 stacked vertically, and a heat roller 40 and a press roller 50 provided on each frame in parallel. The upper frame 120 has a substantially rectangular parallelepiped shape with an open lower surface. The lower frame 130 includes a substantially rectangular bottom plate 131 and side plates 132 erected at both longitudinal ends of the bottom plate 131.

FIG. 3 is a sectional view of the fixing device 30 including the detachable unit 32 as viewed from the downstream side in the transport direction of the recording paper P. The heat roller 40 has a heat source 41 provided inside a hollow roller portion 40a, and a support shaft 42 projects from both ends in the longitudinal direction of the roller portion 40a. The support shaft 42 is held by the radial bearing 43 with respect to the upper frame 120. A heat roller 4 is attached to one end of the support shaft 42.
A roller gear 44 (a driven gear) for rotating 0 is fixed. Note that a description and illustration of a configuration for heating the heat source of the heat roller 40 is omitted.

The press roller 50 is a driven roller that rotates following the heat roller 40 while the recording paper P is pressed against the heat roller 40. Press roller 50
Consists of a fixed support shaft 51 and a cylindrical portion 53 rotatably provided around the fixed support shaft 51 via a radial bearing 52. The cylindrical portion 53 is made of an elastic member such as rubber. . Both ends in the axial direction of the cylindrical portion 53 of the press roller 50 are configured as large diameter portions 55 having a larger outer diameter. The details of the press roller 50 will be described later.

As shown in FIG. 2, an inverted U-shaped groove 123 which is open at the lower end and extends upward is formed on both longitudinal side surfaces of the upper frame 120. The width of the groove 123 is formed to be larger than the outer diameter of the bearing 43 by a predetermined amount. Also, the upper end 13 of the side plate 132 of the lower frame 130
2a has a curved shape along the outer periphery of the bearing 43. Therefore, the bearing 43 is provided in the groove 12 of the upper frame 120.
3 and the upper end 132a of the side plate 132 of the lower frame 130
And held by. On the other hand, the lower frame 130 has a U-shaped groove 133 which is opened at the upper end 132a and extends downward so that the support shaft 51 of the press roller 50 is inserted therethrough.
Are formed. The groove 133 has a width along which the support shaft 51 can move.

As shown in FIG. 3, the fixing device 30 includes an opening / closing mechanism 33 (opening / closing means) for opening and closing the heat roller 40 and the press roller 50, and a heat roller 40.
Is provided. The opening / closing mechanism 33 and the rotation mechanism 34 are attached to the detachable unit 3 from above.
2 is mounted on a base frame 35 having a U-shaped cross section to which the second frame 2 can be mounted. The base frame 35 includes a rectangular bottom plate 36 and a pair of side plates 37 erected at both longitudinal ends of the bottom plate 36. For the heat roller 40 and the press roller 50 which are consumable parts,
The opening / closing mechanism 33, the rotation mechanism 34, and the base frame 35 constitute non-consumable parts in the fixing device 30.

The detachable unit 32 is mounted on the base frame 35 from above, as indicated by the arrow in FIG. FIG.
5 shows a state in which the detachable unit 32 is mounted on the base frame 35. As shown in FIG. 4, when the detachable unit 32 is mounted on the base frame 35, the roller gear 44 of the heat roller 40 is moved to a third
It engages with the gear 147 from above.

FIG. 5 shows the fixing device 30 and the detachable unit 3.
It is a top view showing the state where 2 was removed. Recording paper P
Are indicated by arrows. A motor mounting plate 39 for mounting a fixing drive motor 82 is mounted on one side plate 37 of the base frame 35. The motor mounting plate 39 is provided in parallel with the side plate 37, and the fixing driving motor 82
Are mounted on the motor mounting plate 39 with the output shaft 142 protruding toward the side plate 37. A motor gear 143 is fixed to the output shaft 142. Motor gear 14
3 is a first gear 14 rotatably provided around a support shaft 144 provided between the side plate 37 and the motor mounting plate 39.
5 is engaged. The support shaft 144 is provided with a second gear 146 that rotates integrally with the first gear 145. A third gear 147 (drive gear) rotatably provided on the side plate 37 is engaged with the second gear 146. The third gear 147 engages with the roller gear 44 of the heat roller 40 (FIG. 4).

On the other hand, in addition to the third gear 147, the second gear 146 has a fourth gear rotatably supported by the side plate 37.
Gear 148 is engaged. The fourth gear 148 is engaged with the sixth gear 150 via a fifth gear 149 fixed coaxially. The sixth gear 149 is connected to the camshaft 152 via a clutch 151. That is, by turning on / off the clutch 151, the camshaft 152 is rotated using the driving force of the fixing drive motor 82.

The camshaft 152 is connected to the base frame 3
5 extends between the two side plates 37, 37, and near both ends thereof, a first roller for driving the press roller 50 up and down is provided.
The disc cam 153 and the second disc cam 154 are fixed. An encoder wheel 112 for detecting the rotation angle of the camshaft 152 is fixed to a substantially central portion in the longitudinal direction of the camshaft 152, and the encoder wheel 112 is mounted on the bottom plate 36 of the base frame 35.
A photo-interrupter 113 for reading is formed.

A third disk cam 155 for swinging the swing holder 22 for holding the corona charger 19 of the transfer section 20 (FIG. 1) is fixed substantially at the center of the cam shaft 152. Third disc cam 155
The cam follower 104 provided on a slide arm 23 extending toward the transfer unit 20 is in contact with the cam shaft 152. The rotation of the cam shaft 152 moves the slide arm 23 in the vertical direction in the figure. The details of the swing of the swing holder 22 will not be described.

A discharge roller unit 70 for discharging the recording paper P is provided on the downstream side (lower side in the figure) of the base frame 35 in the transport direction. The paper discharge roller unit 70 includes a pair of upper and lower support shafts 7 extending in the longitudinal direction of the base frame 35.
3, 74, an upper roller 71 as a pair of roller members fixed to the upper support shaft 73, and a lower roller 72 as a pair of roller members fixed to the lower support shaft 74. The rollers 71 and 72 are arranged so as to sandwich the recording paper P from above and below.

A pair of plate members 7 for supporting the support shafts 73 and 74 are provided near both ends in the longitudinal direction of the base frame 35.
7, 77 are erected, and both ends of the support shafts 73, 74 are
It is inserted through holes formed in the plate members 77, 77. A discharge gear 159 is fixed to one end of the support shaft 74 on the rotation mechanism 34 side, and the discharge gear 159 is connected to the third gear via an intermediate gear 158.
It is connected to the gear 147. That is, the fixing drive motor 82
, The lower roller 72 also rotates.

The plate member 7 for inserting both ends of the support shaft 73
The holes 77a, 77a formed in the holes 7, 77 are formed to be long in the up-down direction (direction perpendicular to the paper surface), so that the support shaft 73 can move a predetermined amount in the up-down direction along the holes 77a, 77a. . Both ends of the support shaft 73 are supported from below by a swing lever 75 that is swingably supported by a support shaft 76 provided on the side plate 37. Swing lever 75
Is swingably driven by a swing arm 161 of the opening and closing mechanism 33 which will be described later. That is, the upper roller 71 moves up and down in conjunction with the opening / closing mechanism 33 to open and close the space between the upper roller 71 and the lower roller 72.

Next, the opening / closing mechanism 33 will be described. Support shafts 160 are formed so as to protrude inward from the side plates 37, 37, and a swing arm 161 is swingably supported on the both support shafts 160. A plate 162 integral with the swing arm 161 is provided around the support shaft 160, and the plate 162 has a cam follower 163 that engages with the disc cams 153 and 154.

FIGS. 6A and 6B are side views showing the open / close state of the heat roller 40 and the press roller 50 by the opening / closing mechanism 33. FIG. A tension spring 164 having one end fixed to the bottom plate 36 is attached to the plate 162, and the cam follower 16 is
3 and the disc cams 153 and 154 are always engaged. That is, with the rotation of the disc cams 153 and 154, the swing arm 161 swings due to the engagement between the disc cams 153 and 154 and the cam follower 163. Swing arm 16
The tip of 1 is in contact with the lower side of the support shaft 51 of the press roller 50, and the press roller 50 moves up and down as the arm 161 moves up and down.

When the disc cams 153 and 154 are brought into contact with the cam follower 163 at the maximum radius, the space between the heat roller 40 and the press roller 50 is closed with the recording paper P interposed therebetween (FIG. 6A). The press roller 50 is determined to be the most distant from the heat roller 40 when it comes into contact with the cam follower 163 (FIG. 6B). Thus, by the rotation of the disc cams 153 and 154,
The press roller 50 moves up and down between the operating position and the retracted position.

A guide plate 90 for guiding the recording paper P guided to the fixing device 30 from below is swingably provided in conjunction with the swing arm 161. The guide plate 90 is fixed to a swing member 92 supported by a support shaft 91 provided on the side plate 37. Swing member 91
Is provided with a contact piece 93 that contacts the upper end of the swing arm 161, and a tension spring 94 is provided between the contact piece 93 and the swing arm 161. Therefore, the guide plate 90 swings according to the position of the swing arm 161,
When the swing arm 161 is at the retracted position, the recording paper P is guided so as not to contact with either the heat roller 40 or the press roller 50 (FIG. 6B).

The tip 161a of the swing arm 161
5, comes into contact with a swing lever 75 for opening and closing the upper roller 71 and the lower roller 72 of the discharge roller unit 70. The swing lever 75 is swingably provided by a support shaft 76 provided on the side plate 37.
The support shaft 73 of the upper roller 71 is held on 5.
That is, as the swing arm 161 swings, the upper roller 7
1 swings to open and close between the lower roller 72. Note that the discharge roller unit 70 is omitted in FIG.

Next, a configuration for preventing skew of the recording paper P and jitter will be described. In the printer 1 of the present embodiment, after the heat roller 40 starts rotating, the press roller 50 rises so that the recording paper P does not come into contact with the heat roller 40 in a state where the recording paper P is stopped. .

When the heating of the heat roller 40 is started, the heat roller 40 is heated first, and then the heat roller 4 is heated.
The bearing 43 holding the 0 support shaft 42 is heated, and subsequently the upper frame 120 holding the bearing 43 is heated. Therefore, as shown in FIG. 4, a clearance x is provided between the support shaft 42 and the bearing 43 to absorb the thermal expansion of the support shaft 42 that is heated first. Between them, there is provided a clearance y for absorbing the thermal expansion of the previously heated bearing.

Therefore, when the third gear 147 rotates, the roller gear 44 is urged in the direction of the pressure angle at which the third gear 147 meshes with the roller gear 44, and one end of the heat roller 40 is moved by the clearance (x + y). Can be lifted. That is, the heat roller 40 is inclined with respect to the press roller 50. The fixing device of the present embodiment is configured to prevent skew of the recording paper P and occurrence of jitter due to such inclination of the heat roller 40. Hereinafter, this point will be described.

FIG. 7 is a diagram showing the structure of the press roller 50. As shown in FIG. 7, large-diameter portions 55 having a larger outer diameter are formed at both axial ends of the cylindrical portion 53 of the press roller 50. The distance between the two large-diameter portions 55 is formed larger than the width of the recording paper P. In addition, both large diameter portions 5
5 and a portion between the large-diameter portions 55 are formed larger than the thickness of the recording paper P. In addition, the large diameter portion 5
5, a hollow portion 56 is formed so that the large-diameter portion 55 can be easily deformed and crushed when coming into contact with the heat roller 40.

In the present embodiment, the large-diameter portion 55 is approximately 5 mm from both ends with respect to the cylindrical portion 53 having a total length of 270 mm in the axial direction.
mm, and the width of the recording paper P is 254 m.
m. Further, the outer diameter of the large diameter portion 55 is configured to be larger by 2 to 5 mm than the outer diameter of the cylindrical portion 53 of 40 mm.

FIG. 8 is a schematic diagram showing the open / closed state of the heat roller 40 and the press roller 50. In FIG. 8A,
The heat roller 40 is stopped, and the press roller 50 is at the retract position. When the roller gear 44 is driven, the third
The gear 147 (FIG. 5) and the roller gear 44 mesh with each other to urge the roller gear 44 upward, so that the heat roller 4
One end of 0 rises by the clearance (x + y). That is, the heat roller 40 is inclined (FIG. 8B).

The press roller 50 rises and the heat roller 4
When approaching zero, the large diameter portion 55 of the press roller 50 comes into contact with the surface of the heat roller 40. (FIG. 8 (c)). At this time, the large-diameter portion 55 is attached to the surface of the rotating heat roller 40.
Press roller 50 is connected to the heat roller 4
The rotation follows the rotation of zero.

When the large-diameter portion 55 of the press roller 50 is in contact with the surface of the heat roller 40, the press roller 50 is further raised.
Since it is pushed by the large diameter portion 55 of 0, its end opposite to the roller gear 44 also rises by the clearance x + y (FIG. 8D). That is, the heat roller 40 is parallel to the press roller 50. In this state, the recording paper P is pressed uniformly at a predetermined pressure in the width direction.

As described above, since the large-diameter portions 55 are formed at both ends in the axial direction of the press roller 50, the large-diameter portions 55 of the press roller 50 contact the heat roller 40 to push up the heat roller 40, and the press roller 50 Heat roller 40
Are sandwiched in a state where the recording paper P is parallel to each other. Therefore, the recording paper P is pinched at the same timing in the width direction, and the skew of the recording paper P is prevented.

Further, when the recording paper P is sandwiched between the heat roller 40 and the press roller 50 due to the contact between the heat roller 40 and the large diameter portion 55, the press roller 50
Has already been rotated, so that the recording paper P does not stop during the sandwiching. That is, the jitter caused by the momentary stoppage of the conveyance is prevented.

FIG. 9 shows another example of the shape of the large diameter portion of the press roller. The press roller 250 shown in FIG. 9 is similar to the press roller 50 shown in FIG.
The cylindrical portion 253 is rotatably provided around a bearing 1 via a bearing 252. At both ends in the axial direction of the cylindrical portion 253, the outer diameter increases toward the end (that is, the outer diameter increases).
A large-diameter portion 255 formed (in the shape of a conical skirt) is provided. With this configuration, the large-diameter portion 2
55 can be formed more easily.

FIG. 10 shows a second embodiment of the present invention. In the second embodiment, as shown in FIG.
The press roller 350 does not have a large diameter portion, but has large diameter portions 348 at both ends in the longitudinal direction of the heat roller 340. In the second embodiment, the configuration is the same as that of the first embodiment except for the outer shapes of the heat roller 340 and the press roller 350.

As in the first embodiment, the press roller 35
0 approaches the heat roller 340, the press roller 3
50 urges the heat roller 340 upward through the large-diameter portion 348 (FIG. 10B), and presses the recording paper P in a state where the press roller 350 is parallel to the heat roller 340 (FIG. 10B). FIG. 10 (c)). With such a configuration, in the second embodiment, as in the first embodiment, the occurrence of skew of the recording paper P and occurrence of jitter are prevented.

[0056]

As described above, according to the fixing device of the present invention, when the heat roller and the press roller are brought close to each other, the large diameter portion of the press roller comes into contact with the heat roller to displace the heat roller. After the roller and the press roller are parallel, the recording paper is sandwiched. Accordingly, since the recording paper is simultaneously sandwiched in the width direction, the skew of the recording paper is prevented. Further, since the press roller has already been rotated when the recording paper is sandwiched between the heat roller and the press roller, the recording paper is prevented from stopping during the sandwiching. That is, occurrence of jitter caused by a momentary stoppage of transport is prevented.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a basic configuration of a printer.

FIG. 2 is a perspective view showing a detachable unit in the fixing device.

FIG. 3 is a front view showing an embodiment of a fixing device according to the present invention.

FIG. 4 is a front view showing the fixing device of FIG. 3;

FIG. 5 is a plan view illustrating the fixing device of FIG. 3;

FIG. 6 is a schematic diagram showing an open / close state of a heat roller and a press roller.

FIG. 7 is a diagram showing a shape of a press roller.

FIG. 8 is a schematic diagram showing an open / close state of a heat roller and a press roller.

FIG. 9 is a diagram showing another example of the shape of the press roller.

FIG. 10 is a schematic diagram showing an open / closed state of a heat roller and a press roller according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer 10 Housing 30 Fixing device 32 Detachable unit 34 Rotating mechanism 35 Frame 40,340 Heat roller 42 Support shaft 43 Bearing 44 Roller gear 50,250,350 Press roller 51 Fixed support shaft 52 Bearing 53 Cylindrical portion 55,255 Large diameter portion 82 Fusing drive motor 120 Upper frame 130 Lower frame 152 Camshaft 161 Swing arm 162 Plate 163 Cam follower 348 Large diameter portion

Continued on the front page (72) Inventor Tsutomu Sato 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Gaku Kogyo Co., Ltd. No. 9 Inside Asahi Gaku Kogyo Co., Ltd. (72) Inventor Hiroshi Ishikawa 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Gaku Kogyo Co., Ltd.

Claims (8)

[Claims] 1. A fixing device for fixing an image on recording paper, comprising: a heat roller having a built-in heat source; a press roller for pressing the recording paper between the heat roller; Opening and closing means for relatively moving the heat roller and the press roller to open and close the space between the roller and the press roller, wherein the heat roller is displaceable by a predetermined amount in the direction of the relative movement; The outer diameter of both ends in the axial direction is set to be larger by a predetermined amount than the outer diameter of a portion sandwiched between the both ends, and the interval between the both ends in the axial direction is set to be larger than the width of the recording paper. A fixing device. 2. A fixing device for fixing an image on recording paper, comprising: a heat roller having a built-in heat source; a press roller for pressing the recording paper between the heat roller; Opening and closing means for relatively moving the heat roller and the press roller to open and close between the rollers, holding the heat roller so as to be displaceable by a predetermined amount in the direction of the relative movement, The outer diameter of both ends in the axial direction is formed to be larger by a predetermined amount than the outer diameter of a portion sandwiched between the both ends, and the axial distance between the both ends is set to be larger than the width of the recording paper. A fixing device. 3. The fixing device according to claim 1, further comprising a rotation unit configured to rotate the heat roller before closing the space between the heat roller and the press roller. . 4. A predetermined clearance is provided between a support shaft of the heat roller and a bearing for holding the support shaft, and between the bearing and a holding member for holding the bearing. The fixing device according to claim 1, wherein: 5. The apparatus according to claim 1, wherein the clearance is provided to absorb a difference in thermal expansion between the support shaft, the bearing, and the holding member when the heat roller starts heating. The fixing device according to claim 4. 6. The fixing device according to claim 1, wherein the press roller is positioned vertically below the heat roller. 7. The fixing device according to claim 1, wherein the opening and closing unit moves the press roller in a direction approaching and away from the heat roller. . 8. The fixing device according to claim 1, wherein the heat roller and the press roller are mounted on a frame that is detachable from the fixing device.